Method, device and system for positioning a probe on a target surface in an open cavity in a test object

ABSTRACT

In a method for positioning the end ( 63 ) of a probe ( 60 ) on a target surface inside an open cavity in a test object, preferably on the nasal mucous membrane of a human being, the test object is fixed in a given position, whereupon an optical instrument ( 1 ) is so adjusted that the target surface is located essentially on its optical axis (I) and the position of the target surface in the longitudinal direction of the optical axis is defined. Then, the probe is attached on a holder ( 2 ), which is so operated that the end of the probe is placed essentially on the optical axis and is moved along this axis to the target-surface position defined with the aid of the optical instrument. A device and a system for implementing this method are also disclosed.

FIELD OF THE INVENTION

This invention relates to a method, a device and a system forpositioning a probe on a target surface in an open cavity in a testobject. The open cavity may, for instance, be a body cavity of a humanbeing or an animal, especially the nasal cavity.

BACKGROUND OF THE INVENTION

Occupying an exposed and fairly immovable position directly on the bone,the nasal mucous membrane is a suitable object of study. When studyingthe nasal mucous membrane, one occasionally wishes to insert a probe toa carefully determined position in the nose, for instance in order tointroduce a chemical substance whose effect on the mucous membrane is tobe studied, or in order to carry out a measurement directly on themucous membrane, for instance measure the circulation in the mucousmembrane with the aid of a Doppler laser. In this measurement, the probehas to be placed in a highly exact position in relation to the mucousmembrane. The probe must not, for example, press against the mucousmembrane, since the pressure might then trigger defence mechanismsaltering the circulation. As a result, positioning accuracy in the orderof a tenth of a millimeter or so is required. Owing to tremblings of thehand, hair blocking the view and the darkness in the nasal cavity, itis, of course, extremely difficult to manually position a probe soexactly on the nasal mucous membrane. Consequently, previousmeasurements have not yielded as reliable results as would be desired.

SUMMARY OF THE INVENTION

One object of the invention is, therefore, to provide a method, a deviceand a system enabling highly exact positioning of an end of a probe on agiven location in the nasal cavity.

According to the invention, this object is achieved by a method, adevice and a system having the characteristics recited in appendedclaims 1, 6 and 12, respectively. Preferred embodiments are defined inthe sub-claims.

To be more specific, it has been found that one may perform highly exactpositioning, which in addition can be repeated with a high degree ofrepeatability, by using a combination of optical technique for definingthe place on the mucous membrane where one wishes to position the probeand a device of special design for bringing the probe to this place.

A suitable prior-art optical technique that may be used for implementingthe invention is rhinostereometry, which is described in a doctoralthesis written by Jan-Erik Juto and entitled “Rhinostereometry”, theDepartment of Otorhinolaryngology, Södersjukhuset, Stockholm, 1985,Sweden. A rhinostereometer consists of a microscope which is mounted ona micrometer table. The lens and the eyepiece of the microscope are sochosen as to result in a very shallow depth of field. Today, therhinostereometer is used for measuring the swelling of the nasal mucousmembrane, in which case a small piece of the mucous membrane is observedthrough the microscope and the swelling is measured with the aid of ascale in the eyepiece.

Thus, the rhinostereometer is located outside the cavity to be examined,which is an advantage, it being as problematic to position an opticalinstrument introduced into the nose as to position a probe. In addition,there is not much place for the insertion of an optical instrument, thediscomfort experienced by the patient is accentuated, and there is arisk of hitting the mucous membrane so that this is interfered with,resulting in less exact later measurements.

However, one problem associated with the use of the above opticaltechnique for introducing a probe into the nose is that the spacebetween the lens of the microscope and the nose is restricted, it beingnecessary to place the lens close to the nose in order to obtainsatisfactory light conditions. On the other hand, a probe that is to beinserted in the nose must have an essentially rectilinear and rigid endportion having a length of about 4-5 cm in order that it should bepossible to place its end sufficiently far into the nasal cavity withoutthe remainder of the probe touching the nasal mucous membrane. As aresult, there is in most cases not enough room for the end portion ofthe probe between the rhinostereometer and the nose.

This problem is solved by attaching the end of the probe on apositioning means, which is supported by a stand advantageouslyconsisting of the rhinostereometer, and introducing, in a two-stepoperation, the end of the probe into the nose. In a first step, the endof the probe is brought to a position on or close to the optical axis ofthe rhinostereometer a certain distance into the nose by pivoting thepositioning means about a pivot point located at a distance from theoptical axis and, in a second step, the end of the probe is moved alongthe optical axis until it has come to occupy the position defined withthe aid of the rhinostereometer, more specifically its plane of accuratefocus, by moving the positioning means in parallel with the opticalaxis. Owing to the fact that the positioning means is supported by astand, the problems associated with manual positioning of the probe,e.g. tremblings of the hand with ensuing inaccuracies, are avoided.

In order that the end of the probe should be able to enter the nose, theprobe is suitably turned on the holder in the plane of the pivotalmovement, while the positioning means is pivoted.

To many people, the introduction of an object into a body cavity isassociated with feelings of discomfort. To enable the probe to bebrought directly to the aimed-at position on or close to the nasalmucous membrane, thus minimising the time required for the introduction,a preliminary adjustment without the cooperation of the patient isadvantageously performed. Owing to this preliminary adjustment, the endof the probe may then be directly brought to the right position.

It will be appreciated that the above technique for positioning a probeon the nasal mucous membrane may also be used for positioning a probe inother body cavities of a human being or an animal, for instance in theear or the brain in connection with an operation. This technique mayalso serve to position a probe in other open cavities of an optionalobject. For instance, the probe might be a tube intended for theintroduction of a substance into the cavity, an instrument for taking asample of something in the cavity, or an optical instrument, such as anendoscope, for enlarging some part of the cavity.

One may furthermore consider using other optical techniques thanrhinostereometry. What matters is that one is able to look into the opencavity in order to select a target surface and that the position of thissurface in relation to a reference point, for instance the opticalinstrument used, can be defined with the aid of the technique employed.Moreover, the optical instrument should, as mentioned in the foregoing,be located outside the cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

A few embodiments of the invention will now be described with referenceto the accompanying drawings, in which

FIG. 1 is a schematic perspective view of an embodiment of the inventivesystem, the measurement being performed on a person; and

FIG. 2 is a schematic perspective view similar to that of FIG. 1, exceptfor the fact that the test subject has been replaced with a dummy whichwill be used for the adjustment of the system.

DESCRIPTION OF PREFERRED EMBODIMENTS

For the sake of clarity, FIG. 1 shows the different components(separated along an optical axis I) of a system for positioning a probeon a given location on the nasal mucous membrane of a test subject F.The system according to the invention chiefly comprises arhinostereometer 1, a positioning device 2, a holder 3 for a nose funnel4, and a fixing device 5 for fixing the head of the test subject F insuch a manner that the nasal mucous membrane occupies a fixed positionin space.

The rhinostereometer 1, which can be purchased via AB Micromus, Box10306, S-100 55 Stockholm, Sweden, comprises a surgical microscope, ofwhich only the microscope head 1 a is partly shown in FIG. 1 and whichis so positioned on a micrometer table 1 b as to be movable in threeorthogonal directions, of which two are located in the horizontal plane.The micrometer table 1 b is in turn arranged on a frame 1 c. Themicroscope, which preferably is rotatable in the horizontal plane,comprises a lens and an eyepiece, which are chosen with a view toproviding a shallow depth of field. The well-defined area that can beobserved through the microscope is, in the positioning of the probe,used for defining the target surface of the probe. Conveniently, themicroscope is so oriented that the well-defined area is almostperpendicular to one of the horizontal axes. The eyepiece is providedwith a millimeter scale, which is substantially parallel to the otherhorizontal axis in the system.

The positioning device 2 is adapted to be attached directly on therhinostereometer 1, more specifically on the upper side of themicroscope head 1 a, where three holes 6 are provided in order toreceive three similarly-arranged pins (not shown) provided on thepositioning device. Alternatively, the positioning device may be fixedlyconnected to the frame 1 c of the micrometer table. It is furtherconceivable to attach the positioning device 2 on a separate stand. Itgoes without saying that the position of the positioning device inrelation to the rhinostereometer has to be well-defined. In all cases,the positioning device is thus supported by a stand, either directly orvia the rhinostereometer.

The positioning device comprises a first top plate 7, which ishorizontally arranged and on whose underside the above-mentioned pins 6are provided, and a second top plate 8, which is attached to the firsttop plate 7 by means of an articulation 9 at the edge of the first topplate 7 that, in the direction of the optical axis, is located oppositeto the microscope head. A fine-adjustment screw 10 makes it possible toadjust the angle between the first and the second top plate 7, 8.

A first lateral plate 11 is attached to the one lateral edge of thesecond top plate 8 and extends at an angle of substantially 90° to thetop-plate assembly 7, 8. A second lateral plate 12 is attached to thefirst lateral plate 11 with the aid of an articulation 13, which isplaced at the edge of the first lateral plate 11 that, in the directionof the optical axis, is located opposite to the microscope head. Afine-adjustment screw 14 makes it possible to adjust the angle betweenthe first and the second lateral plate 11, 12.

Instead of being fixedly connected to the second top plate 8, the firstand the second lateral plate 11 and 12 may be movably connected thereto,so that their vertical position in relation to the second top plate 8can be adjusted, for instance with the aid of an adjustment screw.

A first positioning means in the form of a sliding element 16 isslidably mounted in the second lateral plate 12 so as to be displaceablealong a first axis, which is essentially parallel to the optical axis ofthe rhinostereometer. A lever 17 is attached to the second lateral plate12 as well as to the sliding element 16, to enable the latter to beeasily and expediently displaced with the aid of the lever 17. The endposition of the sliding element 16 in the direction away from themicroscope head is defined with the aid of an end position screw 18,which is displaceable in a groove 19 formed in the sliding element 16,and a stop element (not shown) provided on the second lateral plate.

A second positioning means in the form of an arm 20 is pivotally mountedon the end of the sliding element 16 that is located opposite to theend-position screw. The arm 20 can be pivoted about a second axis, whichis perpendicular to the first axis, from a position in which it isessentially parallel to the sliding element to a position in which it isperpendicular thereto. The latter position is defined by a stop element21, which is provided on the sliding element 16 and which prevents thearm 20 from being pivoted any further. The pivotal radius of the arm 20is adjustable with the aid of an adjustment screw 22, which comes intoabutment against a screw 22′, which is screwed into the sliding element16 and constitutes the pivot point of the arm 20. This pivot point maybe displaced in the longitudinal direction of the arm in a slit and belocked with the aid of the adjustment screw 22. The pivot point islocated at a distance from the optical axis.

A probe attachment 23 is so mounted on the end of the arm 20 that islocated farthest away from the sliding element. 16 as to be turnableabout an essentially vertical axis. The attachment 23 is provided with arecess 24 where a probe can be fixed by snap-in action, as illustratedin FIG. 2. The attachment 23 is further equipped with a lever 25, bymeans of which it can be easily and expediently turned in the pivotalplane of the arm 20.

On the arm 20, there is further provided an element 26 for fixing theattachment lever 25. This fixing element 26 extends transversely of thelongitudinal direction of the arm 20 and has a recess 27, in which theattachment lever 25 can be fixed. The position of the fixing element inthe transverse direction in relation to the arm 20 can be adjusted withthe aid of an adjustment screw 28, a fine adjustment of the angularposition of the attachment being obtainable.

The positioning device has an alignment axis I which is parallel to thesliding element 16. When the device is mounted on the rhinostereometer,the alignment axis I should essentially coincide with the optical axisof the rhinostereometer.

Further, the fixing device 5 comprises a stand 30, on which is fixedlymounted an acrylic splint 31 individually designed for each patient.With the aid of the acrylic splint 31, the test subject, or to be morespecific the head of the test subject and, hence, his nasal mucousmembrane, can be fixed in a given position in space or a coordinatesystem. Preferably, the fixing device 5 is fixedly connected to theframe 1 c of the rhinostereometer by means of a connecting element 32,so that the patient may repeatedly be placed in one and the sameposition in relation to the frame 1 c of the rhinostereometer.

The holder 3, which preferably is attached on the fixing device 5,comprises an articulated arm 35 on which is mounted the nose funnel 4,which may be a conventional ear speculum or a nasal speculum. Thearticulated arm 35 may either be movable in a versatile manner, suchthat the articulation elements are freely movable in relation to eachother, or be fixed with the aid of an adjustment screw 40, such that thearticulation elements are fixed in relation to each other.

The system illustrated in FIG. 1 operates as follows. When a probe is tobe positioned on or adjacent to the nasal mucous membrane of a patient,the head of the patient F is first fixed in space or in a coordinatesystem with the aid of the fixing device 5 by having the patient biteinto the acrylic splint 31 of individual design. In order to widen thenostril slightly and keep aside hair and mucus, the nose funnel 4 isthen introduced into the nostril into which the probe is later to beinserted.

In the next step, the person conducting the examination looks throughthe rhinostereometer and chooses a target surface on the nasal mucousmembrane by moving and pivoting the rhinostereometer so that the targetsurface comes to be located in its plane of accurate focus. When this isthe case, the position of the nose funnel 4 is locked with the aid ofthe adjustment screw 40, as is the position of the rhinostereometer onthe micrometer table 1 b. In addition, one notes the position of thetarget surface on the scale in the eyepiece. Preferably, therhinostereometer is so directed that the target surface is located atthe centre of the millimeter scale, i.e. on the optical axis. However,it may, in some applications, be necessary or suitable to place thetarget surface at a small distance from the optical axis.

At this stage, the optical axis has been fixed, and the position of thetarget surface has been defined in relation to the rhinostereometer orin a coordinate system where the rhinostereometer serves as the originof coordinates. The patient may then let go of the acrylic splint 31 andremove his nose from the nose funnel 4. The acrylic splint is thenremoved from the fixing device and replaced with a target-surface dummy50 (shown in FIG. 2), which comprises a T-shaped element 51 that isformed with a groove 52 in the body 53 of the T and an auxiliary targetsurface 54 that is provided with a point of aim 56 and extendsperpendicular to the plane of the T-shaped element 51 and is movablealong the crossbar 55 of the T. The position of the auxiliary targetsurface 54 on the crossbar 55 of the T is so adjusted as to be locatedon the optical axis I of the rhinostereometer, and the attachment pointfor the target-surface dummy in the groove 52 is so adjusted that theauxiliary target surface 54 is located in the plane of accurate focus ofthe rhinostereometer and the point of aim 56 is located at the centre ofthe scale of the rhinostereometer. When this adjustment has been made,the auxiliary target surface thus occupies the same position in space aswas previously occupied by the target surface on the nasal mucousmembrane when the patient was fixed with the aid of the acrylic splint31. However, the auxiliary target surface is by no means necessary, andthe adjustment described in the following may also be performed bylooking through the rhinostereometer to observe when the end of theprobe has reached the correct position.

In the next step, a probe 60 is, as illustrated in FIG. 2, attached tothe probe attachment 23 by snap-in action. When this happens, the arm ispivoted to a position in which it is almost parallel to the slidingelement 16 and the pivot point 22′ is adjusted to a position a certaindistance in on the arm 20, such that the pivotal radius thereof is notmaximal. The probe 60 comprises a rectilinear and rigid end portion 61,which is connected to a hose 62. The outermost end 63 of the end portion61 should be slightly angled to enable it to be applied against aninclined surface. When the probe 60 has been attached by snap-in action,the arm 20 is pivoted on the sliding element 16. During this pivotalmovement, the attachment lever 25 is movable, enabling the attachment 23to be turned on the arm 20. During this pivotal movement, the pivotalradius of the arm 20 further increases until the arm comes into abutmentagainst the stop element 21 on the sliding element 16. In this position,the end of the probe is located a certain distance into the nose funnel4. Then, the attachment lever 25 is fixed on the fixing element 26. Theposition of the attachment 23 perpendicular to the sliding element isadjusted with the aid of the adjustment screw 22 on the arm 20, suchthat the probe end 63 is located essentially on the optical axis, andthe angular position of the attachment 23 is finely adjusted with theaid of the adjustment screw 28 on the fixing element 26, such that theprobe end 63 is located in the recorded place on the scale of theeyepiece and the remainder of the end portion of the probe is locatedessentially in parallel with the optical axis.

The position of the probe end in relation to the optical axis havingbeen thus determined, the sliding element 16 is, with the aid of thelever 17, moved in the direction of the auxiliary target surface 54.When approaching the auxiliary target surface 54, the probe end 63 canbe seen through the rhinostereometer. If need be, one may then perform afine adjustment of the position of the probe end in relation to theoptical axis with the aid of the adjustment screws 22 and 28, whereuponthe probe end 63 is applied against the auxiliary target surface 54 onthe point of aim 56 with the aid of the lever 17. The position of thesliding element 16 when the probe end occupies this position isregistered by moving the end-position screw 18 in the groove 19 so thatit comes to be applied against the stop (not shown) and is fixed. Thepositioning device has now been pre-set to enable the probe end 63 to bebrought directly to the correct position on the nasal mucous membrane ofthe patient.

The sliding element 16 is then withdrawn with the aid of the lever 17,the arm 20 is pivoted away, and the attachment lever 25 is unfixed toenable the probe 60 to be moved out of the nose funnel 4 and away fromthe optical axis I. The holder 3 for the nose funnel is rendered movablein a versatile manner, and the target-surface dummy 50 is replaced withthe patient's acrylic splint 31, whereupon the patient anew has to biteinto the splint so that the target surface on the nasal mucous membraneis once more fixed in the position it had when the rhinostereometer wasadjusted. Then, the nasal funnel 4 is once more introduced into thepatient's nostril and so positioned that the optical axis is located atthe centre of the nose funnel.

The probe end 63 may now easily and expediently be placed in the correctposition on the nasal mucous membrane by pivoting the arm 20 until itcomes to be applied against the stop element 21 on the sliding element16, attaching the attachment lever 25 on the stop element 26, andbringing the sliding element 16 with the aid of the level 17 to the endposition defined by the end-position screw 18.

If the degree of swelling of the nasal mucous membrane alters during themeasurement in the nose, the position of the probe end 63 perpendicularto the optical axis can be adjusted with the aid of the fine-adjustmentscrew 14 on the lateral-plate assembly 11, 12.

When the positioning device is put to use, the second top plate 9 ispreferably angled somewhat in relation to the first top plate 8, so thatthe longitudinal axis of the sliding element 16 is angled somewhat inthe vertical plane in relation to the optical longitudinal axis, suchthat it is only the end 63 of the probe that is located directly on theoptical axis, the remainder of the rigid end portion of the probe beingslightly angled in relation to the optical axis in the vertical plane.In this manner, the probe end will not be hidden by the remainder of theprobe.

As an alternative to the mode of operation described above, thepre-setting can be performed without the patient taking part at all. Onethen begins by adjusting the rhinostereometer in relation to theauxiliary target surface of the target-surface dummy, so that thissurface comes to be located in the plane of accurate focus of therhinostereometer. (The fixing device has been moved aside and is notused). Then, the probe 60 is fixed on the attachment 23 on the arm 20,which may be pivoted to the position perpendicular to the slidingelement 16, since the nose funnel 4 is not in the way. The attachmentlever 25 is fixed on the fixing device, and the arm 20 is moved inparallel with the optical axis with the aid of the sliding element 16,so that the end 63 of the probe 60 come3 to be applied against theauxiliary target surface 54. When the probe end is close to theauxiliary target surface 54, it can be seen through therhinostereometer, and its position can be finely adjusted with the aidof the adjustment screws 28 and 22. When the probe end 63 occupies theaimed-at position, the position of the sliding element 16 is registeredwith the aid of the screw 18. The pre-setting operation has now beencompleted. When the probe end is to be positioned on the patient, thetarget-surface dummy 50 is replaced with an acrylic splint which thepatient bites into. The nasal funnel 4 is introduced into the patient'snostril and is fixed. The rhinostereometer is so adjusted that thetarget surface on the patient is visible in the plane of accurate focus.Unless the optics of the rhinostereometer have been adjusted, the targetsurface is now located in the same position in relation to therhinostereometer as was previously occupied by the auxiliary targetsurface. Since the positioning device is fixedly connected to therhinostereometer, the probe end 63 may now be positioned on the targetsurface by pivoting the arm 20, fixing the attachment lever 25 on thefixing device 27, and moving the sliding element 16 to the positiondefined by the adjustment screw 18.

It goes without saying that the above embodiments and modes of operationare but examples, which can be modified in many ways within the scope ofthe appended claims. For instance, the positioning device need not bepre-set, the probe end being then positioned directly on the nasalmucous membrane by means of the positioning device.

What is claimed is:
 1. A method for positioning an end of a probe on atarget surface inside an open cavity in a test object, comprising thesteps of fixing the test object in a given position; adjusting anoptical instrument in such a manner that the target surface is locatedessentially on its optical axis and the position of the target surfacein the longitudinal direction of the optical axis is defined; attachingthe probe on a pivotable arm, which is supported by a stand; causing thepivotable arm to perform a pivotal movement about a pivot point locatedat a distance from the optical axis, such that the end of the probe ispositioned essentially on the optical axis a certain distance into theopen cavity; and thereafter moving the pivotable arm in parallel withthe optical axis, such that the end of the probe reaches thetarget-surface position defined with the aid of the optical instrument.2. A method as claimed in claim 1, comprising the further steps ofturning the probe on the pivotable arm in the plane of the pivotalmovement while causing the pivotable arm to perform the pivotalmovement.
 3. A method as claimed in claim 2, comprising the furthersteps of removing the test object from the given position after theoptical instrument has been adjusted; and, after the end of the probehas been moved to the target-surface position defined by the opticalinstrument, recording the position of the pivotable arm, moving thepivotable arm such that the end of the probe will no longer be locatedin the target-surface position defined by the optical instrument, againfixing the test object in the given position, and moving the end of theprobe to the target-surface position defined by the optical instrumentby operating the pivotable arm to the recorded position.
 4. A method asclaimed in claim 2, comprising the further steps of, before the testobject is fixed in a given position, so adjusting the optical instrumentthat an auxiliary target surface occupies a defined position in thelongitudinal direction on the optical axis of the instrument, carryingout the attachment of the probe on the pivotable arm, operating thepivotable arm in such a manner that the end of the probe is located onthe auxiliary target surface, recording the position of the pivotablearm, moving the pivotable arm so that the end of the probe no longer islocated on the auxiliary target surface, and removing the auxiliarytarget surface, the adjustment of the optical instrument after the testobject has been fixed in a given position being carried out in such amanner that the target surface is placed in the same position inrelation to the optical instrument as was previously occupied by theauxiliary target surface, and the pivotal movement of the pivotable armand the displacement of the pivotable arm in parallel with the opticalaxis being performed with the aid of the recorded position of thepivotable arm.
 5. A method as claimed in claim 1, comprising the furthersteps of removing the test object from the given position after theoptical instrument has been adjusted; and, after the end of the probehas been moved to the target-surface position defined by the opticalinstrument, recording the position of the pivotable arm, moving thepivotable arm such that the end of the probe will no longer be locatedin the target-surface position defined by the optical instrument, againfixing the test object in the given position, and moving the end of theprobe to the target-surface position defined by the optical instrumentby operating the pivotable arm to the recorded position.
 6. A method asclaimed in claim 5, comprising the further steps of placing, after thetest object has been removed from the given position, an auxiliarytarget surface on the optical axis and displacing this target surfaceuntil it reaches the target-surface position defined by the opticalinstrument.
 7. A method as claimed in claim 1, comprising the furthersteps of, before the test object is fixed in a given position, soadjusting the optical instrument that an auxiliary target surfaceoccupies a defined position in the longitudinal direction on the opticalaxis of the instrument, carrying out the attachment of the probe on thepivotable arm, operating the pivotable arm in such a manner that the endof the probe is located on the auxiliary target surface, recording theposition of the pivotable arm, moving the pivotable arm so that the endof the probe no longer is located on the auxiliary target surface, andremoving the auxiliary target surface, the adjustment of the opticalinstrument after the test object has been fixed in a given positionbeing carried out in such a manner that the target surface is placed inthe same position in relation to the optical instrument as waspreviously occupied by the auxiliary target surface, and the pivotalmovement of the pivotable arm and the displacement of the pivotable armin parallel with the optical axis being performed with the aid of therecorded position of the pivotable arm.
 8. A device for positioning anend of a probe on a target surface inside an open cavity in a testobject, the device being intended for use along with an opticalinstrument, the device being adapted to define a position of the targetsurface, the device being adapted to be supported by a stand and havingan alignment axis which essentially coincides with the optical axis ofthe optical instrument when the device is in use, the device comprising:a sliding element which is displaceable along a first axis that isparallel to the alignment axis of the device, and a pivotable arm whichis connected to the sliding element and on which is provided anattachment for the probe, the pivotable arm being pivotable in relationto the sliding element about a second axis which is perpendicular to thefirst axis, such that the attachment can be brought to a positionessentially on the alignment axis, wherein there are provided means forestablishing the position of the attachment on the pivotable arm.
 9. Adevice as claimed in claim 8, wherein the device is adapted to besupported by the optical instrument.
 10. A system for positioning an endof a probe on a target surface inside an open cavity in a test object,wherein there are provided a device for fixing the test object in agiven position, an optical instrument for defining the position of thetarget surface, and a device for positioning an end of the probe on thetarget surface inside the open cavity in the test object, the devicebeing intended for use along with the optical instrument, the devicebeing adapted to define a position of the target surface, the devicebeing adapted to be supported by a stand and having an alignment axiswhich essentially coincides with the optical axis of the opticalinstrument when the device is in use, the device comprising a slidingelement displaceable along a first axis parallel to the alignment axisof the device, and a pivotable arm connected to the sliding element andon which is provided an attachment for the probe, the pivotable armbeing pivotably attached to the sliding element by a member having asecond axis which is perpendicular to the first axis, such that thepivotable arm is pivotable only in a single plane perpendicular to thesecond axis and the attachment can be brought to a position essentiallyon the alignment axis, said device being attached to the opticalinstrument in such a manner that its alignment axis coincides with theoptical axis of the optical instrument.
 11. A system as claimed in claim10, wherein the optical instrument comprises a microscope, which ismounted on a frame in such a manner as to be displaced in threeorthogonal directions, the position of the target surface being definedby displacing the microscope so that the target surface is located inthe place of accurate focus of the microscope.
 12. A system as claimedin claim 11, wherein there is provided an auxiliary target surface whichis attachable on the fixing device.
 13. A system as claimed in claim 10,wherein there is provided an auxiliary target surface, which isattachable on the fixing device.